I have a spare room in my house which would be ideal for a studio as it is large and has its own door.

The problem is that the room faces a main street (a five lane parkway with two service roads) and has two large windows which let in a lot of nosie - even when closed.

Would I get a significant reduction of outside noise if I installed an extra layer of windows? And if so, what kind of glass and what thickness should I use? Also how much space should I leave for the dead air between the two windows? Is plexiglass good?

I have another room I could use which is about 8 decibals quieter - but I'd rather use the front room if I can bring down the sound. Your suggestions?

Thanks,
Chony